# infra/units/flyedge.service — pushed to /etc/systemd/system/flyedge.service.
#
# The feed WebSocket served from flysim's feed bus (docs/design/flybus.md,
# "Feed over the bus"; services/flysim/crates/fly-edge). DISABLED BY DEFAULT:
# it is in no target's Wants=/Requires= and 07-enable.sh does not enable it.
# With FLY_FEED_VIA=direct (the default, written into /etc/fly/fly.env by
# 05-deploy.sh) flysim binds 127.0.0.1:7400 itself and this unit has nothing
# to do. To move the feed onto the bus on one container:
#
#   1. FLY_FEED_VIA=bus in the env file, then 05-deploy.sh (rewrites fly.env);
#   2. systemctl enable --now flyedge.service; systemctl restart flysim.service
#      (flysim stops binding :7400, the edge binds it once the first snapshot
#      is on the bus);
#   3. nothing for the watchdog: check 2 reads FLY_FEED_VIA from fly.env and
#      follows the feed counters to this unit's loopback /metrics.
#
# Back: FLY_FEED_VIA=direct, deploy, systemctl disable --now flyedge.service,
# restart flysim.
#
# Ordering (docs/design/flybus.md, amendment "Feed store lifecycle"): flysim
# owns the router and its store under /run/fly/bus, so it starts first and
# the edge follows it. Requires= makes an explicit stop or restart of flysim
# (the unstick rule's `systemctl restart flysim.service` included) stop or
# restart the edge with it. A crash-restart of flysim is covered by the edge
# itself: it drops its clients, unbinds :7400 and reconnects every 500 ms,
# so nothing here has to be restarted by hand. The edge holds no state; the
# store is flysim's and a new router removes the previous one's directory.
[Unit]
Description=flyedge: the feed WebSocket served from flysim's feed bus
After=flysim.service
Requires=flysim.service
# A release that predates fly-edge has no binary; stay cleanly inactive
# rather than restart-looping (the flybridge.service header explains why a
# Condition, not a start limit).
ConditionPathExists=/opt/fly/current/fly-edge

[Service]
Type=simple
User=fly
# FLY_FEED_VIA, FLY_BUS_DIR and the rest of flysim's configuration: the edge
# reads the same file so the two cannot disagree about the port or the bus.
EnvironmentFile=/etc/fly/fly.env
Environment=FLY_FEED_BIND=127.0.0.1:7400
Environment=FLY_BUS_DIR=/run/fly/bus
# Its own read-only /metrics and /healthz, for watchdog check 2 in bus mode.
# Loopback only: nothing off the container needs the edge's counters.
Environment=FLY_EDGE_METRICS_ADDR=127.0.0.1:9102
ExecStart=/opt/fly/current/fly-edge
Restart=always
RestartSec=2
# A few snapshots in flight and a WebSocket per client; the store itself is
# flysim's (tmpfs, bounded by feedbus::limits at 32 MiB).
MemoryMax=256M

[Install]
WantedBy=fly.target